Generally, in a home location register (HLR) of a mobile communication system, each process includes an application service element (ASE) for processing protocol relevant messages and other messages, a process management block (PRMB) for performing periodical process' health check, queue check, and lock file check with respect to the ASE, and an operation & maintenance subsystem (OMS) for managing the PRMB.
The PRMB largely comprises a health check algorithm, a queue check algorithm, an overload algorithm, and a process state management algorithm. The PRMB checks existence and validity of a process related to the relevant mobile communication system during initialization before performing the algorithms.
Subsequently, the health checks, the queue check, the lock file check, the process by the OMS, and other processes for the messages are recurrently performed.
The health check algorithm checks health of each ASE included by the system and processes faults, if the faults are happened. The PRMB checks the health while transmitting and receiving messages to and from each ASE or through file locking.
The overload algorithm checks whether or not queues in each process are overloaded. The overload designates that the amount of messages lead into the queue of a process exceeds 65,535 bytes and messages stored in the entire process amount to over 120,000 bytes or the number of the message amounts to over 24,000.
A method of controlling the overload uses use time of the process as a reference of the overload, which is disclosed in the U.S. Pat. No. 4,974,256 entitled "Load Balancing and Overload Control in a Distributed Processing Telecommunications System". This method is to periodically measure real time occupancy of each processor and allocate new calls in such a way as to attempt to make each processor's occupancy approach the average occupancy of all the processors. When the average occupancy of the processors in one period exceeds a predetermined value, this is detected as overload. If the overload happens, new calls are shed to make the average occupancy not exceed the predetermined value.
Another method of controlling the overload, which is disclosed in the U.S. Pat. No. 4,809,318, is to detect the overload based upon the number of connected calls and the number of calls which are waiting to be handled by a process and to reject new requests under the overload.
Further another method of controlling the overload, which is disclosed in the U.S. Pat. No. 4,511,762, is to detect the overload based upon the time for a process to transmit a message to a line and trunk and receive a response message.
However, conventional technology of controlling the overload is developed with a focus on hardware of an exchange, so it has problems in detecting and controlling the overload occurring in a communication system with basis of a common computer. The overload can be caused by various factors, such as an amount of entire messages and converge of messages into a particular process in the communication system. In this regard, the conventional technology is lacking in precisely detecting the overload occurring in the overall system.